1. Field of the Invention
This invention pertains generally to a method for improving the performance of electrokinetic pumps that produce high pressures by converting electric potential to hydrodynamic force. More particularly, by manipulating the surface charge or zeta potential of a porous dielectric material used in these electrokinetic pumps, this invention provides a method for eliminating gas bubble induced blocking of current flow, and consequent pump failure, caused by electrolytic decomposition of the electrolyte.
2. Description of the Related Art
It has been demonstrated that it is possible, by means of a process called electrokinetic pumping, to produce hydraulic pressures in excess of 5000 psi by the application of a voltage gradient along a porous dielectric in contact with a conductive electrolyte material using at least two spaced electrodes, as shown in FIG. 1. A detailed discussion of the electrokinetic pumping process can be found in prior co-pending U.S. Pat. No. 6,013,164 and entitled ELECTROKINETIC HIGH PRESSURE HYDRAULIC SYSTEM, assigned to the same assignee. In electrokinetic pumping, an electric potential on the order of hundreds to thousands of volts, well above the potential required for electrolytic decomposition of any electrolyte, is required to develop the desired high pressures. Electrolytic decomposition of the electrolyte results in gas generation and the gas generated at the high pressure side of an electrokinetic pump can form bubbles that can block the current flow required for pressure generation, causing pump failure. This condition is particularly troublesome in miniaturized applications, such as in capillary tubes or microchannels, an area where the use of hydraulic pressure for manipulation of liquids holds great promise, but where current flow can be easily blocked. What is needed is a means for eliminating blocking current flow by bubble formation in electrokinetic pumping applications or providing for any gas generated to be removed from the system before operational complications are created.